Configuring A Secondary Root Switch - Cisco Catalyst 2950 Software Configuration Manual

Chapter 10 Configuring STP
We recommend that you avoid manually configuring the hello time, forward-delay time, and
Note
maximum-age time by using the spanning-tree vlan vlan-id hello-time, spanning-tree vlan vlan-id
forward-time, and the spanning-tree vlan vlan-id max-age global configuration commands after
configuring the switch as the root switch.
Beginning in privileged EXEC mode, follow these steps to configure a switch as the root switch:
Command
Step 1 configure terminal
Step 2 spanning-tree vlan vlan-id root primary
[diameter net-diameter [hello-time seconds]]
Step 3
end
Step 4
show spanning-tree detail
Step 5
copy running-config startup-config
To return the switch to its default setting, use the no spanning-tree vlan vlan-id root global
configuration command.

Configuring a Secondary Root Switch

When you configure a Catalyst 2950 switch that supports the extended system ID as the secondary root,
the switch priority is modified from the default value (32768) to 28672. The switch is then likely to
become the root switch for the specified VLAN if the primary root switch fails. This is assuming that
the other network switches use the default switch priority of 32768 and therefore are unlikely to become
the root switch. For Catalyst 2950 switches without the extended system ID support (software earlier
than Release 12.1(9)EA1), the switch priority is changed to 16384.
You can execute this command on more than one switch to configure multiple backup root switches. Use
the same network diameter and hello-time values as you used when you configured the primary root
switch with the spanning-tree vlan vlan-id root primary global configuration command.
78-11380-04
Purpose
Enter global configuration mode.
Configure a switch as the root switch.
• For vlan-id, the range is 1 to 4094 when the enhanced
software image is installed and 1 to 1005 when the
standard software image is installed. Do not enter leading
zeros.
(Optional) For diameter net-diameter, specify the
•
maximum number of switches between any two end
stations. The range is 2 to 7.
• (Optional) For hello-time seconds, specify the interval in
seconds between the generation of configuration messages
by the root switch. The range is 1 to 10 seconds; the
default is 2 seconds.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Catalyst 2950 Desktop Switch Software Configuration Guide
Configuring Spanning-Tree Features
10-13